Watercraft are often powered by an outboard motor positioned at their stern. The outboard motor has an internal combustion engine positioned within a cowling, the engine arranged to power a water propulsion device of the motor.
The motor is normally mounted to the watercraft to permit the motor to be moved independent of the watercraft in both the horizontal and vertical directions. To promote easy movement of the motor and so that the motor does not contribute to significant air drag, the motor is generally designed to be extremely compact.
In order for the motor to be compact, its cowling must be small, reducing the internal engine space. The components of the engine are thus placed very close together, and the space between the engine and the cowling is minimal. So arranged, the substantial heat generated by the engine is to a large degree trapped in the cowling and transmitted to the engine components.
In order to improve emission quality and fuel economy, fuel may be supplied to the engine powering an outboard motor with one or more fuel injectors. The fuel supply system for such an engine is generally arranged so that fuel is supplied from a supply under high pressure to the injector.
When this type of fuel injected engine is used to power an outboard motor, several problems result. First, the high temperatures in the cowling exacerbate vapor creation in the fuel system. Vapor in the fuel reduces the effectiveness or efficiency of the pump which is used to pressurize the fuel to a high pressure. When either the pressure or volume of fuel supplied is reduced, the efficiency of the fuel injection system is compromised.
In addition, difficulties arise in using a single pump for moving the fuel from the supply to the injector(s) and for pressurizing the fuel. This single pump must be excessively large or be arranged to sacrifice delivery capacity in favor of providing fuel under high pressure.
It is, therefore, an object of the present invention to provide an improved fuel supply for an engine of the type used in a marine application.